Ink-jet ink compositions

ABSTRACT

A water-dissipatable polymer having colorant attached thereto through a covalent —O-link and an ink comprising the water-dissipatable polymer and a liquid medium.

This application is the National Phase of International ApplicationPCT/GB99/04209 filed Dec. 13, 1999 which designated the U.S. and thatInternational Application was published under PCT Article 21(2) inEnglish.

This invention relates to coloured water-dissipatable polymers, to inkscontaining the coloured water-dissipatable polymers and to their use inink jet printing.

Ink jet printing methods involve a non-impact printing technique forprinting an image onto a substrate using ink droplets ejected through afine nozzle onto a substrate without bringing the nozzle into contactwith the substrate.

There are many demanding performance requirements for colorants and inksused in ink jet printing. For example they desirably provide sharp,non-feathered images having good water-fastness, light-fastness andoptical density. The inks are often required to dry quickly when appliedto a substrate to prevent smudging, but they should not form a crustover the tip of an ink jet nozzle because this will stop the printerfrom working. The inks should also be stable to storage over timewithout decomposing or forming a precipitate which could block the finenozzle. The most popular ink jet printers are thermal and piezoelectricink jet printers.

There is a need for inks which are suitable for both thermal and piezoink jet printers, have high colour strength and produce images having ahigh light-fastness and water-fastness when printed on a substrate.

We have surprisingly found that the coloration of water-dissipatablepolymers having hydroxy functional groups by reacting the hydroxyfunctional groups with a colorant, a bridging group for a colorant or acolorant precursor and further reaction of the bridging compound with acolorant or colorant precursor and subsequent conversion of the colorantprecursor to a colorant, gives a coloured water-dissipatable polymerwhich is suitable for use in inks for thermal and piezo ink jetprinters.

According to a first aspect of the present invention there is provided awater-dissipatable polymer having colorant attached thereto through acovalent —O-link.

A —O-link may be exemplified by but is not limited to the followinglinks such as an ether link (R¹—O—R², an ester link (R¹—O—C(O)—R²) and aphosphate ester link (R¹—O—P(O)(OH)—R²), where R¹ represents thewater-dissipatable polymer and R² represents the colorant.

A water-dissipatable polymer of the invention is obtainable by attachinga colorant to a water-dissipatable polymer having hydroxy functionalgroups by means of a reaction between the hydroxy functional groups onthe polymer with a colorant having a functional group capable ofreacting with the hydroxy functional group.

The colorant may also be attached to the water-dissipatable polymer bymeans of a reaction between a hydroxy group on the polymer with acolorant precursor thereby forming a covalent bond therebetween andsubsequently converting the colorant precursor to a colorant.

Alternatively, colorants may be grafted to the water-dissipatablepolymer via a bridging compound. For example, colorant may be attachedto the water-dissipatable polymer by means of a reaction between thehydroxy functional group on the water-dissipatable polymer with abridging compound thereby forming a covalent bond therebetween andsubsequently reading the bridging compound with a colorant or colorantprecursor. The bridging agent may be a di-, tri-, tetra- orpolyfunctional structure, and examples include, but are not limited tobis alkyl halides, tris dialkyl halides, bis acid chlorides, tris diachlorides, bis vinyl sulphones, tris divinyl sulphones, mixtures ofalkyl halides and acid chlorides, michael acceptors, cyanuric chlorideand related reactive 1,3,5-triazines, other reactive heterocyclichalides and aromatic halides. Most preferably cyanuric chloride is used.

The water-dissipatable polymer of the invention is preferably preparedby condensing a water-dissipatable polymer having hydroxy functionalgroups with a colorant having a functional group reactive towards thehydroxy functional groups. Such functional groups are described above.Up to 100%, preferably at least 95%, more preferably at least 90%, mostpreferably at least 85% of the hydroxy functional groups are reactedwith the colorant. The condensation is performed by preparing a solutionor suspension of a water-dissipatable polymer having hydroxy functionalgroups in an aqueous and/or non-aqueous solvent. Preferably thecondensation is performed at a pH of 5 to 14, more preferably of 6 to13, especially of 7 to 12. The condensation is preferably performed inthe presence of an inorganic or organic base. Preferred inorganic basesare NaOH, KOH, Na₂CO₃, K₂CO₃. Preferred organic bases are trialkylamines, 1,5-diazabicyclo[4.3.0]non-5-ene (DBN),1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), and1,4-diazabicyclo[2.2.2]octane (DABCO). Subsequently an aqueous solutionof a colorant is added to the suspension and the mixture is stirreduntil the reaction is complete.

Alternatively a non-aqueous grafting reaction can be used to react thewater-dissipatable polymer having hydroxy functional groups with acolorant. The colorant and polymer are stirred in a non-aqueous solventwith a base (either homogeneous or heterogeneous) and heated as requiredto complete the reaction. In the case of ester formation, for examplereacting an acid functionalised colorant (e.g. phosphoric acidfunctionalised) and the water-dissipatable polymer having hydroxyfunctional groups, conditions are required to remove the generated watereither physically (e.g. by azeotroping, molecular sieves) or chemicallyusing a dehydrating agent such as dicyclohexylcarbodiimide ordicyandiamide. Acid catalysts such as p-toluenesulphonic acid orsulphuric acid may also be employed.

The water-dissipatable polymer of the invention may be isolated from theaqueous system by either acidification and filtration; dilution with awater miscible solvent and filtration, salting out with organic salts orsolutions of organic salts or combinations of these methods. Suitablesalts include sodium chloride, ammonium chloride, sodium sulphate andlithium chloride. Alternatively the mixture is acidified until thewater-dissipatable polymer of the invention precipitates out or thesolvent is evaporated or the solvent is diluted with water until thewater-dissipatable polymer of the invention precipitates out.

Alternatively the water-dissipatable polymer of the present inventionmay be purified by ion-exchange methods on cationic resins. Otheroptions include the removal of low molecular weight materials such asco-solvents used for the polymerisation, low molecular weight salts,impurities and free monomers by ultra-filtration, osmosis, reverseosmosis, dialysis, ultra-filtration or a combination thereof, followedby evaporation of the water.

Preferably the number average molecular weight (Mn) of thewater-dissipatable polymer used to make the polymer of the invention isless than 25,000, more preferably is less than 20,000, especially lessthan 15,000. The Mn of the polymer may be measured by gel permeationchromatography (“gpc”).

The gpc method used for determining Mn preferably comprises applying thepolymer to a chromatography column parked with cross-linkedpolystyrene/divinyl benzene, eluting the column with tetrahydrofuran ata temperature of 40° C. and assessing the Mn of the polymer compared toa number of a polystyrene standards of a known Mn. Suitable cross-linkedpolystyrene/divinyl benzene chromatography columns are commerciallyavailable from Polymer Laboratories.

As an alternative to the gpc method for determining Mn, the Mn may bedetermined using for example by multi-angle light scattering (MALLS).

The water-dissipatable polymer may be a copolymer, for example a random,alternating or block copolymer, preferably a random copolymer.

The water-dissipatable polymer may be a polyurethane, polyester or anolefinic polymer. Preferably the water-dissipatable polymer is anolefinic polymer. An olefinic polymer is a polymer obtainable from thepolymerisation of one or more olefinically unsaturated monomers.

The water-dissipatable olefinic polymer is preferably obtainable fromthe polymerisaton of one or more olefinically unsaturated monomershaving hydroxy functional groups, and one or more olefinicallyunsaturated monomers having water-dispersing groups optionally in thepresence of one or more olefinically unsaturated monomers which are freefrom water-dispersing groups.

Preferred olefinically unsaturated monomers having hydroxy functionalgroup(s) include, but are not limited to, hydroxy-functional esters ofacrylic acid, methacrylic acid, maleic acid, or fumaric acid. Examplesof such monomers include hydroxy functional alkyl (preferably 1 to 18 C)(meth)acrylates such as 2-hydroxy ethylacrylate, 2-hydroxyethylmethacrylate, 2-hydroxy propylacrylate, 3-hydroxy propylacrylate,2-hydroxy propylmethacrylate, 3-hydroxy propylmethacrylate, 4-hydroxybutylacrylate, 4-hydroxy butylmethacrylate, hydroxy stearylacrylate,hydroxy stearylmethacylate; dihydroxy alkyl (preferably 1 to 6 C)adducts of maleic acid, fumaric acid, and phthalic acid; polyethyleneoxide or polypropylene oxide functionalised hydroxyl functional(meth)acrylate such as the commercially available material known asBISOMER PPM5S, BISOMER PPM6E (International Specialty Chemicals);Caprolactone acrylate monomers such as the commercial available materialknown as TONE M100 Monomer (Union Carbide). Other examples include(4-hydroxymethyl cyclohexyl)-methylacrylate (Mitsubishi Chemical); andBlemmer PE-90, Blemmer PE-200, and Blemmer PE-350 (polyethylene glycolmethacylates of molecular weights 163-173, 261-303 and 387-468respectively); Blemmer 70 PEP-350B (CH₂═C(CH₃—C(═O)—(EO), (PO)³)—H whereEO is polyethylene oxide, PO is polypropylene oxide and the molecularweight is about 450); and Blemmer-GLM (glycerol dimethacrylate) (allNippon Oil and Fats Co.); N-methylol acrylamide, glycerolmonomethacrylate and trimethylol propane mono methacylate.

Olefinically unsaturated monomers having a hydroxy functional group alsoincludes olefinically unsaturated monomers having a group which isconvertible to a hydroxy functional group and include but are notlimited to vinyl acetate, vinyl benzoate, vinyl benzyl chloride, vinylbromide and vinyl chloride.

Water-dispersing groups provide the facility of self-dispersibility andsolubility to the polymer in ink media, especially in water. Thewater-dispersing groups may be ionic, non-ionic or a mixture of ionicand non-ionic water-dispersing groups. Preferred ionic water-dispersinggroups include basic amine groups, cationic quaternary ammonium groupsand acid groups, for example phosphoric acid groups, sulphonic acidgroups and carboxylic acid groups.

The water-dispersing groups may be incorporated into the polymer in theform of monomers or oligomers bearing the appropriate water-dispersinggroups. One may also react a polymer which is not water-dissipatablewith monomers or oligomers which make the polymer water-dissipatable.

The nature and level of water-dispersing groups in the polymerinfluences whether a solution, dispersion, emulsion or suspension isformed on dissipation of the water-dissipatable polymer.

The water-dispersing group content of the water-dissipatable polymer mayvary within wide limits but is preferably sufficient to make thewater-dissipatable polymer form stable ink-jet printing inks in waterand aqueous media.

The acid water-dispersing groups may be subsequently fully or partiallyneutralised with a base containing a cationic charge to give a salt. Ifthe acid water-dispersing groups are used in combination with anon-ionic water-dispersing group, neutralisation may not be required.The conversion of any free acid groups into the corresponding salt maybe effected during the preparation of the water-dissipatable polymerand/or during the preparation of an ink from the water-dissipatablepolymer.

Preferably the base used to neutralise any acid water-dispersing groupsis ammonia, an amine or an inorganic base. Suitable amines are tertiaryamines, for example triethylamine or triethanolamine. Suitable inorganicbases include alkaline hydroxides and carbonates, for example lithiumhydroxide, sodium hydroxide, or potassium hydroxide. A quaternaryammonium hydroxide, for example N⁺(CH₃)₄OH⁻, can also be used. Generallya base is used which gives the required counter ion desired for the inkwhich is prepared from the polymer. For example, suitable counter ionsinclude Li⁺, Na⁺, K⁺, NH₄ ⁺ and substituted ammonium salts.

Preferred olefinically unsaturated monomers providing ionicwater-dispersing groups include acrylic acid, methacrylic acid, itaconicacid, maleic acid, monoalkyl itaconates (for example, monomethylmaleate, monoethyl maleate, monobutyl maleate and monooctyl maleate),citraconic acid, styrenesulfonic acid, vinylbenzylsulfonic acid,vinylsulfonic acid, acryloyloxyalkyl sulfonic acids (for example,acryloyloxymethyl sulfonic acid, acryloyloxyethyl sulfonic acid,acryloyloxypropyl sulfonic acid and acryloyloxybutyl sulfonic acid),methacryloyloxymethyl sulfonic acid, methacryloyloxyethyl sulfonic acid,methacryloyloxypropyl sulfonic acid and methacryloyloxybutyl sulfonicacid), 2-acrylamido-2-alkylalkane sulfonic acids (for example2-acrylamido-2-nethylethanesulfonic acid,2-acrylamido-2methylpropanesulfonic acid and 2-acrylamido-2-methylbutanesulfonic acid), 2-methacrylamido-2-alkylalkane sulfonic acids (forexample, 2-methacrylamido-2-methylethanesulfonic acid,2-methacrylamido-2-methylpropanesulfonic acid and2-methacrylamido-2-methylbutanesulfonic acid),mono-(acryloyloxyakyl)phosphates (for example,mono(acryloyloxyethyl)phosphate and mono(3-acryloyloxypropyl)phosphates)and mono(methacryloyloxyalkyl)phosphates (for example,mono(methacryloyloxyethyl)phosphate andmono(3-methacryloyloxypropylphosphate).

Non-ionic water-dispersing groups may be in-chain, pendant or terminalgroups. Preferably non-ionic water-dispersing groups are pendantpolyoxyalkylene groups, more preferably polyoxyethylene groups. Thenon-ionic water-dispersing groups may be introduced into thewater-dissipatable polymer in the form of a compound bearing non-ionicwater-dispersing groups and at least one (although preferably only one)copolymerisable olefinically unsaturated group.

Preferred olefinically unsaturated monomers providing non-ionicwater-dispersing groups include alkoxy polyethylene glycol(meth)acrylates, preferably having a number average molecular weight offrom 350 to 2000. Examples of such monomers which are commerciallyavailable include ω-methoxypolyethylene glycol (meth)acrylate anddiethylene glycol mono vinyl ether.

In addition to the water-dissipatable polymer comprising olefinicallyunsaturated monomers having a hydroxy functional group or a group whichis convertible to a hydroxy functional group, and one or moreolefinically unsaturated monomers having water-dispersing groups, thewater-dissipatable polymer may also contain one or more olefinicallyunsaturated monomers which are free from water-dispersing groups and/orhydroxy functional groups.

Preferred olefinically unsaturated monomers which are free fromwater-dispersing groups include alkyl(meth)acrylates, optionallysubstituted styrenes, methacrylamides, allyl compounds, dienes, vinylethers, vinyl ketones, vinyl halides, vinylidene halides, olefins andunsaturated nitriles.

Preferred alkyl(meth)acrylates contain less than twenty carbon atoms.Examples include methyl acrylate, ethyl acrylate, n-propyl acrylate,isopropyl acrylate, n-butyl acrylate, isobutyl, sec-butyl acrylate, amylacrylate, hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate,tert-octyl acrylate, 2-phenoxyethyl acrylate, 2-chloroethyl acrylate,2-bromoethyl acrytate, 4-chlorobutyl acrylate, cyanoethyl acrylate,2-acetoxyethyl acrylate, dimethylaminoethyl acrylate, benzyl acrylate,methoxybenzyl acrylate, 2-chlorocyclohexyl acrylate, acylate, cyclohexylacylate, furfuryl acrylate, tetrahydrofurfuryl acrylate, phenylacrylate, 5-hydroxypentyl acrylate, 2,2-dimethyl-3-hydoxypropylacrylate, 2-methoxyethyl acrylate, 3-methoxybutyl acrylate,2-ethoxyethyl acrylate, 2-iso-propoxyethyl acrylate, 2-butyoxyethylacrylate, 2-(2-methoxyethoxy)ethyl acrylate, 2-(2-butoxyethoxy)ethylacrylate, 1-bromo-2-methoxyethyl acrylate, 1,1-dichloro-2-ethoxyethylacrylate, methyl methacrylate, ethyl methacrylate, n-propylmethacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutylmethacrylate, sec-butyl methacrylate, amyl methacrylate, hexylmethacrylate, cyclohexyl methacrylate benzylmethacrylate, chlorobenzylmethacrylate, octyl methacrylate, N-ethyl-N-phenylaminoethylmethacrylate, 2-(3phenylpropyloxy)ethyl methacrylate,dimethylaminophenoxyethyl methacrylate and furfuryl methacrylate.Aromatic examples include but are not limited to 4-alkyl phenylacrylateor methacrylate, phenyl methacrylate, phenyl acrylate, and β-napthylmethacrylate,

Preferred optionally substituted styrenes include styrene,methylstyrene, dimethylstyrene, trimethylstyrene, ethylstyrene,diethylstyrene, isopropylstyrene, butylstyrene, hexylstyrene,cyclohexylstyrene, decylstyrene, chloromethylstyrene,trifluoromethylstyrene, ethoxymethylstyrene, acetoxymethylstyrene,methoxystyrene, 4-methoxy-3-methylstyrene, dimethoxystyrene,chlorostyrene, dichlorostyrene, trichlorostyrene, tetrachlorostyrene,pentachlorostyene, bromostyrene, dibromostyrene, iodostyrene,trifluorostyrene and 2-bromo-4-tri-fluoromethylstyrene.

Preferred methacrylamides contain less than 12 carbon atoms. Examplesinclude methylmethacrylamide, tert-butylmethacrylamide,tert-octylmethacrylamide, benzylmethacrylamide, cyclohexylmethacylamide,phenylmethacrylamide, dimethylmetharylamide, dipropylmethacrylamide,hydroxyethyl-N-methylmethacrylamide, N-methylphenylmethacrylamide,N-ethyl-N-phenylmethacrylamide and methacrylhydrazine.

Preferred allyl compounds include allyl acetate, allyl caproate, allylcaprylate, allyl laurate, allyl palmitate, allyl stearate, allylbenzoate, allyl acetoacetate, allyl lactate, allyloxyethanol, allylbutyl ether and allyl phenyl ether.

Preferred vinyl ethers contain less than 20 carbon atoms. Examplesinclude methyl vinyl ether, butyl vinyl ether, hexyl vinyl ether, octylvinyl ether, decyl vinyl ether, ethylhexyl vinyl ether, methoxyethylvinyl ether, ethoxyethyl vinyl ether, chloroethyl vinyl ether,1-methyl-2,2-dimethylpropyl vinyl ether, 2-ethylbutyl vinyl ether,hydroxyethyl vinyl ether and dimethylaminoethyl vinyl ether.

Preferred vinyl ketones contain less than 12 carbon atoms. Examplesinclude methyl vinyl ketone, phenyl vinyl ketone and methoxyethyl vinylketone.

Preferred vinyl halides include vinyl chloride, vinylidene chloride andchlorotrifluoro ethylene.

Preferred olefins include unsaturated hydrocarbons having less than 20carbon atoms. Examples include dicyclopentadiene, ethylene, propylene,1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene,1-decene, 5-methyl-1-nonene, 5,5-dimethyl-1-octene, 4-methyl-1-hexene,4,4-dimethyl-1-pentene, 5-methyl-1-hexene, 4-methyl-1-heptene,5-methyl-1-heptene, 4,4-dimethyl-1-hexene, 5,5,6-trimethyl-1-heptene,1-dodecene and 1-octadecene.

Preferred unsaturated nitrites include arylonitrile andmethacyrlonitrile.

The preferred olefinically unsaturated monomers which are free fromwater-dispersing groups are the alkyl (meth)acrylates containing lessthan 20 carbon atoms, especially those specifically listed above.

Preferably the water-dissipatable olefinic polymer is an acrylicpolymer. An acrylic polymer is preferably a polymer formed from amonomer system comprising at least 40 weight % (more preferably at least50 weight %) of one or more monomers of formula

CH₂═CR²COOR³

where R² is H or methyl and ZR³ is optionally substituted alkyl of 1 to12 carbon atoms or cycloalkyl of 5 to 12 (more preferably 1 to 8 and 5to 8 carbon atoms respectively), examples of which have been givenherein.

The water-dissipatable olefinic polymer may be prepared in aconventional manner by polmerising the olefinically unsaturated monomershaving water-dispersing groups and olefinically unsaturated monomershaving a hydroxy functional group or a group which is convertible to ahydroxy functional group, either alone or in the presence ofolefinically unsaturated monomers which are free from water-dispersingand hydroxy functional groups. Temperatures of from 20° C. and 180° C.are preferred. The polymerisation may be continued until reactionbetween the monomers is complete.

In one embodiment the olefinic water-dissipatable polymer may beprepared by polymerising an acrylic oligomer having water-dispersinggroups and at least one olefinically unsaturated terminal group in thepresence of one or more olefinically unsaturated monomers having ahydroxy functional group or a group which is convertible to a hydroxyfunctional group, and optionally one or more olefinically unsaturatedmonomers which are free from water-dispersing groups and/or one or moreolefinically unsaturated monomers having water-dispersing groups.

Alternatively an acrylic oligomer with at least one olefinicallyunsaturated terminal group and which is free from water-dispersinggroups may be polymerised in the presence of one or more olefinicallyunsaturated monomers having a hydroxy functional group or a group whichis convertible to a hydroxy functional group and one or moreolefinically unsaturated monomers having water-dispersing groups.

Preferred polymerisation methods include solution polymerisation,emulsion polymerisation, suspension polymerisation andsolution/dispersion polymerisation and such general methods as are wellknown in the art. More preferably aqueous or non-aqueous solutionpolymerisation and emulsion polymerisation is used and most preferablysolution polymerisation is used.

If desired, an initiator may be used to assist the water-dissipatableolefinic polymer formation. Suitable initiators are free-radicalgenerators. Examples of catalysts include azobis compounds, peroxides,hydroperoxides, redox catalysts, etc., for example, potassiumpersulfate, ammonium persulfate, tert-butyl peroctoate, benzoylperoxide, isopropyl percarbonate, 2,4-dichlorobenzoyl peroxide, methylethyl ketone peroxide, cumene hydroperoxide, dicumyl peroxide,azobisisobutyronitrile, azobis(2-amidino-propane)hydrochloride and thelike.

Typically 0.05 to 5% by weight of initiator is used relative to thetotal weight of the monomers. Preferably the polymerisation is performedin the presence of an emulsifying agent.

The molecular weight of the olefinic water-dissipatable polymer may becontrolled by the addition of chain transfer agents and/or through theadjustment of the ration of the concentration of monomers relative tothe concentration of initiator during the course of the polymerisation.Typical chain transfer agents are thiols, halocarbons and cobaltmacrocycles.

When the water-dissipatable polymer is a polyester or polyurethane itmay be prepared by conventional techniques, for example as described inWO99/50364 (polyurethanes) or WO98/59007 (polyesters) using a monomercarrying a protected hydroxy functional group to form thewater-dissipatable polymer followed by removal of the protecting groupprior to reaction with a colorant, a colorant precursor, or a bridgingcompound to give a covalent —O-link.

When the water-dissipatable polymer is prepared by the polymerisation of(a) monomers having hydroxy functional groups or a group which isconvertible to a hydroxy functional group, and (b) monomers providingwater-dispersing groups optionally in the presence of (c) monomers whichare free from water-dispersing groups and hydroxy functional groups, itis preferred that the amount of (a) is from 1 to 95%, more preferablyfrom 2 to 90% and the amount of (b) is from 1 to 95%, more preferablyfrom 5 to 90% and the amount of (c) is from 0 to 95%, more preferablyfrom 5 to 90% by weight, wherein (a)+(b)+(c) add up to 100.

The water-dissipatable polymer preferably has an acid value of from 0 to750 mgKOH/g, more preferably 50 to 450 mgKOH/g, especially 50 to 225mgKOH/g.

Suitable colorants include reactive dyes. Reactive dyes are known in theart as dyes as having functional groups reactive towards hydroxyfunctional groups. These reactive dyes include, but are not limited to:i) chlorine or fluorine containing reactive dyes, for example dichloroand monochloro triazine reactive dyes, ii) vinyl sulphone or protectedvinyl sulphone reactive dyes for example sulphato ethyl sulphonereactive dyes, iii) aziridine functionalised dyes, iv) epoxidefunctionalised dyes, v) isocyanate functionalised dyes and vi)phosphoric acid functionalised dyes which give ester links ondehydration.

The colorant preferably has at least one functional group capable ofreacting with a hydroxy functional group on the water-dissipatablepolymer. If two or more such functional groups are present in thecolorant, one preferably has a higher reactivity than the other(s) toprevent undesirable cross-linking which results in a non-desirableviscosity increase, making the water-dissipatable polymer less suitablefor thermal ink-jet printing inks. Examples of suitable functionalgroups include alkyl halides, acid chlorides or bromides, reactive aryland heterocyclic halides, esters, acids (if a catalyst and/or adehydrating agent is used), reactive olefins and masked reactive olefins(for example vinyl sulphones or acrylates), isocyanates,isothiocyanates, epoxides, aziridenes, tosylates, mesylates and othersulphone leaving groups. The functional group may be present in thecolorant or grafted to the colorant via a bridging compound.

The colorant preferably has a chromophoric group comprising an azo,anthraquinone, pyrroline, phthalocyanine, polymethine, aryl-carbonium,triphenodioxazine, benzodifuranone or indolene group. Preferredchromophoric groups are azo groups, especially monoazo, disazo, tisazoand phthalocyanine groups.

The colorant may be a single coloured component or a mixture of colouredcomponents, for example it may be a mixture of different dyes. By usinga mixture of different dyes as the colorant one may achieve greaterflexibility in colour of the ink. The colorant may also comprise acolorant precursor. For example the colorant precursor may be convertedto a colorant by a process comprising a diazotisation reaction. Adiazotisation reaction suitably comprises the steps:

(i) diazotising an amino group in the colorant precursor using adiazotising agent; and

(ii) coupling the product of step (i) with a coupling component formingan azo group therebetween.

Preferably the colorant is soluble in organic solvents and/or water,especially water. More preferably the dyes are water soluble anionic orcatonic dyes. Most preferably an anionic dye is used to graft onto ananionic water-dissipatable polymer and a cationic dye is used to graftonto a cationic water-dissipatable polymer. Water solubility of the dyemay be achieved by the presence of acidic or basic groups in the dye.Preferred acidic groups are phosphonic, carboxylic or sulphonic acids,and combinations and salts thereof.

In a second aspect of the present invention there is provided an inkcomprising the components:

(a) a water-dissipatable polymer according to the first aspect of thepresent invention; and (b) a liquid medium.

Preferably the ink comprises from 0.5 to 50 parts of component (a) andfrom 50 to 99.5 parts of component (b), wherein all parts are by weightand the number of parts of (a)+(b)=100. The number of parts of component(a) is preferably from 0.5 to 28, more preferably from 2 to 25, andespecially from 2.5 to 20 parts. Preferably component (b) compriseswater and an organic solvent. More preferably component (b) comprisesfrom 40 to 95 parts, more preferably from 50 to 90 parts of water; andfrom 2 to 60 parts, more preferably from 3 to 50 parts, especially from5 to 35 parts of water-miscible organic solvent. Preferably component(a) is completely dissipated in component (b).

The number of parts of component (a) (the water-dissipatable polymer ofthe invention) is calculated on a 100% solids basis. For example 50 g ofa water-dissipatable polymer of the invention in a 20% solids w/wdispersion is taken as 10 g of component (a).

The inks according to the second aspect of the invention may be preparedby mixing the water-dissipatable polymer of the invention with a liquidmedium. Suitable techniques are well known in the art, for exampleagitation, ultrasonication or stirring of the mixture. The mixture ofwater-dissipatable polymer of the invention and liquid medium may be inthe form of a dispersion, emulsification, suspension, solution ormixture thereof.

The liquid medium is preferably water, a mixture of water and an organicsolvent and an organic solvent free from water. For example thewater-dissipatable polymer of the invention may be added to waterfollowed by the addition of one or more organic solvents. Preferably thewater-dissipatable polymer of the invention is mixed with a liquidmedium, comprising a mixture of water and one or more organic solvents.

When the liquid medium comprises a mixture of water and an organicsolvent, the weight ratio of water to organic solvent is preferably from99:1 to 1:99, more preferably from 99:1 to 50:50, especially from 95:5to 80:20 and most preferably 90:10.

It is preferred that the organic solvent present in the mixture of waterand organic solvent is a water-miscible organic solvent or a mixture ofsuch solvents.

Suitable water-miscible organic solvents include C₁₋₅-alkanols, e.g.methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol,tert-butanol and isobutanol; amides, e.g. dimethytormamide anddimethylacetamide; ketones and ketone alcohols, e.g. acetone anddiacetone alcohol; C₂₋₄-ether, e.g. tetrahydrofuran and dioxane;alkylene glycols or thioglycols containing a C₂-C₆ alkylene group, e.g.ethylene glycol, propylene glycol, butylene glycol, pentylene glycol andhexylene glycol; poly(alkyleneglycol)s and thioglycol)s, e.g. diethyleneglycol, thiodiglycol, polyethylene glycol and polypropylene glycol;polyols, e.g. glycerol and 1,2,6-hexanetriol; and lower akyl glycol andpolyglycol ethers, e.g. 2-methoxyethanol, 2-(2-methoxyethoxy)ethanol,2-(2-ethoxyethoxy) ethanol, 2-(2-butoxyethoxy)ethanol,3-butoxypropan-1-ol, 2[2-(2-methoxyethoxy)-ethoxy]ethanol,2-[2-(2-ethoxyethoxy)ethoxy]-ethanol; cyclic esters and cyclic amides,e.g. optionally substituted pyrrolidones; sulpholane; and mixturescontaining two or more of the aforementioned water-miscible organicsolvents. Preferred water-miscible organic solvents are C₁₋₆-alkyl monoethers of C₂₋₆-alkylene glycols and C₁₋₆-alkyl mono ethers ofpoly(C₂₋₆-alkylene glycols).

Suitable water-immiscible organic solvents include aromatichydrocarbons, e.g. toluene, xylene, naphthalene, tetrahydronaphthaleneand methyl naphthalene; chlorinated aromatic hydrocarbons, e.g.chlorobenzene, fluorobenzene, chloronaphthalene and bromonaphthalene;esters, e.g. butyl acetate, ethyl acetate, methyl benzoate, ethylbenzoate, benzyl benzoate, butyl benzoate, phenylethyl acetate, butyllactate, benzyl lactate, diethyleneglycol dipropionate, dimethylphthalate, diethyl phthalate, dibutyl phthalate, di (2-ethylhexyl)phthalate; alcohols having six or more carbon atoms, e.g. hexanol,octanol, benzyl alcohol, phenyl ethanol, phenoxy ethanol, phenoxypropanol and phenoxy butanol; ethers having at least 5 carbon atoms,preferably C₅₋₁₄ ethers, e.g. anisole and phenetole; nitrocellulose,cellulose ether, cellulose acetate; low odour petroleum distillates;turpentine; white spirits; naphtha; isopropylbiphenyl; terpene;vegetable oil; mineral oil; essential oil; and natural oil; and mixturesof any two or more thereof. Benzyl alcohol is especially preferred.

The ink optionally contains a biocide, for example Proxel GXL (Proxel isa trade mark of Avecia Limited) or Kathon (Kathon is a trade mark ofRohm and Haas), a fungicide, a rheological agent, e.g. a wax (e.g.beeswax), a clay (e.g. bentonite), an IR absorber, for example Projet900NP (Projet is a trade mark of Avecia Limited), or a fluorescentbrightener, for example C.I. Fluorescent Brightener 179 and/or UVabsorber, for example hydroxy phenylbenzotriazole. Furthermore the inkoptionally contains a surface active agent, wetting agent and/or anemulsifier, for example those described in McCutcheon's Emulsifiers andDetergents 1996 International Edition or in Surfactants Europa 3^(rd)Edition 1996 each of which is incorporated herein by reference. In apreferred embodiment the ink of the present invention does not containany pigments.

The ink preferably has a pH from 3 to 11, more preferably from 4 to 10.The pH selected will depend to some extent on the desired cation forcolorant and the material used to construct the ink jet printer head.The desired pH may be obtained by the addition of an acid, base or pHbuffer. Where a base is used this is preferably the same base as wasused to neutralise any anionic dispersing group during the preparationof the water-dissipatable polymer of the invention.

The viscosity of the ink is preferably less than 20 mPa.s (cP), morepreferably less than 15 mPa.s (cP), especially less than 10 mPa.s(cP),at 20° C.

Preferably the ink has been filtered through a filter having a mean poresize below 10 μm, preferably below 5 μm, more preferably below 2 μm,especially below 0.45 μm. In this way particulate matter is removedwhich could otherwise block fine nozzles in an ink jet printer.

Preferably the ink contains less than 500 ppm, more preferably less than250 ppm, especially less than 100 ppm of in total of divalent andtrivalent metal ions.

The inks of the present invention have the advantage that they aresuitable not only for the use in piezoelectric ink jet printer but alsoin thermal and continuous ink jet printers. Many other inks based onpolymers work poorly or even not at all in thermal ink jet printers.

Inks of the present invention form discrete droplets on the substratewith little tendency for diffusing. Consequently sharp images withexcellent print quality and little if any bleed between colours printedside by side can be obtained. Furthermore the inks show good storagestability, wet and light fastness and fastness to both acidic andalkaline highlighter pens.

A third aspect of the invention provides a process for printing an imageon a substrate comprising applying thereto an ink according to thesecond aspect of the present invention by means of an ink jet printer.

The ink jet printer preferably applies the ink to the substrate in theform of droplets which are ejected through a small nozzle onto thesubstrate. Preferred ink jet printers are piezoelectric ink jet printersand thermal ink jet printers. In thermal ink jet printers, programmedpulses of heat are applied to the ink in a reservoir by means of aresistor adjacent to the nozzle, thereby causing the ink to be ejectedin the form of small droplets directed towards the substrate duringrelative movement between the substrate and the nozzle. In piezoelectricink jet printers the oscillation of a small crystal causes ejection ofthe ink from the nozzle.

The substrate is preferably a paper, plastic, or textile material, morepreferably a paper, an overhead projector slide or a textile material,especially paper.

Preferred papers are plain, coated or treated papers which may have anacid, alkaline or neutral character. Most preferably the substrate is acoated paper.

According to a fourth feature of the invention there is provided an inkjet printer cartridge, optionally refillable, containing an ink ashereinbefore defined.

The invention will now be described by example only. All parts andpercentages are by weight unless specified otherwise. In the examples,compounds referred to by reference to Cl numbers are the dyestuffsidentified by these numbers in the Colour Index International, 3^(rd)Edition, 3^(rd) Revision.

Abbreviations used herein:

MAA = methyl acrylic acid MAA = methyl methacrylate HEMA = hydroxy ethylmethacrylate EHA = ethyl hexylacrylate Sty = styrene EA = ethyl acrylateAIBN = azo-iso-butylnitrile β-CEA = β-carboxylate ethyl acrylate HPA =hydroxy propylacrylate AA = acrylic acid

Preparation of Water-dissipatable Polymer 1 Carrying Hydroxy FunctionalGroups MAA/MMA/HEMA/EHA/EA=15/34/10/10/31

using components as listed in Table 1 below and where Formula 1represents a repeat unit of 2-hydroxyethylmethacrylate (HEMA) wheren=10% w/w of the water-dissipatable polymer.

TABLE 1 Formula 1

Component Number Component Weight (g) 1 Azo-iso-Butylnitrile (AIBN) 0.62 Butyl-3-Mercaptopropionate 7.0 3 Methyl Ethyl ketone 333.5 4 MethylAcrylic Acid (MAA) 35.0 5 Methyl Methacrylate (MMA) 79.6 6 Hydroxy EthylMethacrylate (HEMA) 23.3 7 Ethyl Hexyl Acrylate (EHA) 23.3 8 EthylAcrylate (EA) 71.9 9 Azo-iso-Butylnitrile (AIBN) 1.7 10 Methyl Ethylketone 30.0

The initial charge (components 1,2,3,4,5,6,7 and 8) were added to astirred reaction vessel under a nitrogen atmosphere and heated to 80° C.The initiator feed (components 9 and 10) was charged to a 50 ml syringe.At 80° C. the initiator feed was added slowly to the initial chargemixture via the use of a syringe pump such that the total addition timewas three hours. When the addition of the initiator feed was completed,the reaction mixture was left to stir for one hour at 90° C. A monomer‘burn-up’ was then carried out by adding V65 initiator 0.2% on solids(V65=2,2-azobis(2,4-dimethylvaleronitrile CAS 4419-11-8, V65 is a tradename of Wako) and leaving for a further 40 minutes at 90° C. The productwas then cooled to room temperature before being bottled.

The solution of the Water-dissipatable Polymer 1 was found to have asolids content of 40.0%. Molecular weight distribution was done on theWater-dissipatable Polymer 1 by gel permeation chromatography givingMw=10550 and Mn=4760. Purification of the Water-dissipatable Polymer 1was carried out to remove any un-reacted monomer. 10 parts of thewater-dissipatable polymer was dissolved in 100 parts of aqueous ammonia(pH 9), cascade filtered and reverse osmosis was carried out until a lowconductivity (<100 μs) was achieved.

EXAMPLE 1 Preparation of Coloured Water-dissipatable Polymer 1

A suspension of the Water-Dissipatable Polymer 1 (9 parts) in water (50parts) at room temperature was adjusted to pH 9.5 by addition of 2Nsodium hydroxide solution. The mixture was stirred for 2 hours and thena solution of Cl Reactive Red 11 (30 parts) in water (200 parts) wasadded dropwise over 10 minutes whilst maintaining pH 9.5 by dropwiseaddition of 2N sodium hydroxide. The solution was left to stir at pH 9.5and room temperature for 60 hours and then adjusted to pH 1 by additionof excess 2N hydrochloric acid. The resulting solid was isolated byfiltration and washed with copious distilled water. The solid wasdissolved in aqueous ammonia, precipitated by acidification to pH 1 with2N hydrochloric acid, isolated by filtration and washed with distilledwater. The dissolving, isolation and precipitation process was thenrepeated twice.

The resultant coloured water-dissipatable polymer was dissolved inaqueous ammonia and the solution was filtered through a cascade offilters (Glass microfibre GF/A, GF/F and membrane) to 0.45 micron andthen purified by reverse osmosis using a 3000 MW cut off membrane andevaporated to dryness at approximately 80° C. to give ColouredWater-dissipatable Polymer 1 containing a repeat unit of Formula 2:

Preparation of Ink

Inks were prepared by dissolving 10% of the Coloured Water-dissipatablePolymer 1 in a stock solution of 9 parts water and 1 part1-methyl-2-pyrrolidinone with the addition of concentrated ammonia togive a pH of 9-10. The inks were then filtered through a 0.45 micronmembrane filter and printed using an HP 560 thermal IJ printer. Thefollowing results (Table 2) were obtained on Gilbert Bond paper:

TABLE 2 Example 1 OD Run down % solid in ink Optical Density a b (5 min)10 0.362 +33.01 −16.92 10 10 0.720 +54.63 −19.47  9

The resultant prints had excellent fastness to acidic and alkalinehighlighter pens.

Preparation of a Colorant of Formula 3 Comprising a Dye and a BridgingCompound

para-Aminobenzenesulfatoethylsulfone (8 parts) was added to a stirredsolution of Cl Reactive Red 11 (20 parts) in water (80 parts) at roomtemperature and the resulting solution was adjusted to pH 7.0 byaddition of 2N sodium hydroxide. The solution was allowed to stir at pH7.0 and room temperature overnight and then salt was added until a solidprecipitated. The resulting suspension was filtered and the collectedcoloured paste was washed with brine.

The coloured paste was dissolved in distilled water and the solution wasfiltered through a cascade of filters (Glass microfibre GF/A, GF/F andmembrane) to 0.45 micron and then purified by reverse osmosis using a500 MW cut off membrane and evaporated to dryness on a rotary evaporatorat 40° C. to leave the colorant of Formula 3 (13 parts)

EXAMPLE 2 Preparation of Coloured Water-dissipatable Polymer 2

A suspension of the Water-dissipatable Polymer 1 in water (5 parts) atroom temperature was adjusted to pH 12 by addition of 2N sodiumhydroxide solution. The mixture was stirred for 2 hours and the colorantof Formula 3, as prepared above (1 part) was added and the solution wasreadjusted to pH 12. The resulting solution was stirred at pH 12 androom temperature for 72 hours and then adjusted to pH 1 by addition ofexcess 2N hydrochloric acid. The resulting solid was isolated byfiltration and washed with copious distilled water. The solid wasdissolved in aqueous ammonia, precipitated by acidification with 2Nhydrochloric acid, isolated by filtration and washed with distilledwater. The dissolving, isolation and precipitation process was thenrepeated again.

The resultant coloured water-dissipatable polymer was dissolved inaqueous ammonia and the solution was filtered through a cascade offilters (Glass microfibre GF/A, GF/F and membrane) to 0.45 micron andthen purified by reverse osmosis using a 3000 MW cut off membrane andevaporated to dryness at approximately 80° C. to give the ColouredWater-dissipatable Polymer 2 containing a repeat unit of Formula 4:

Preparation of Ink

An ink was prepared by dissolving 10% of the Coloured Water-dissipatablePolymer 2 in a stock solution of 9 parts water and 1 part1-methyl-2-pyrrolidinone with the addition of concentrated ammonia togive a pH of 9-10. The ink was then filtered through a 0.45 micronmembrane filter and printed using an HP 560 thermal Ink-Jet printer. Thefollowing results (Table 3) were obtained on Gilbert Bond paper

TABLE 3 Example 2 Run Down % Solid in Ink OD a b (5 min) 10 0.738 +31.07−17.66 10

The resultant print had excellent fastness to acidic and alkalinehighlighter pens. The print lost 5% OD on fading for 100 hours in anaccelerated light fastness test.

Preparation of a iso-Nonylamine Salt of a Colorant of Formula 5

iso-Nonylamine (6 parts) was dissolved in distilled water (150 parts)and set stirring. A solution of a dye base of Cl Reactive Red 11 sodiumsalt (5 parts) in water (50 parts) was screened through a GF/F filterand added dropwise over 30 minutes to the solution of iso-nonylamine,maintaining pH 7.0 by addition of 2N hydrochloric acid. The mixture wasstirred for 30 minutes and then the resulting suspension was filtered togive a paste. The collected paste was washed with water (20 parts) andthen dried at room temperature and under reduced pressure overphosphorus pentaoxide for 24 hours to leave a red solid colorant ofFormula 5.

EXAMPLE 3 Preparation of Coloured Water-dissipatable Polymer 3

Cyanuric chloride (1.3 parts) and potassium carbonate (1 part) wereadded to a stirred solution of Water-dissipatable Polymer 1 (10 parts)in tetrahydrofuran (110 parts) at room temperature. The resultingmixture was stirred for 2 hours and then a solution of the colorant ofFormula 5 (130 parts), triethylamine (1.1 parts) andN,N-dimethylaminopyridine (0.2 parts) in dimethylformamide (260 parts)was added in one portion. The solution was left to stir for 60 hours andthen pored onto vigorously stirred water (3000 parts). The resultingprecipitate was collected by filtration and washed with copiousdistilled water. The solid was dissolved in aqueous ammonia,precipitated by acidification with 2N hydrochloric acid, isolated byfiltration and washed with distilled water. The dissolving, isolationand precipitation process was then repeated again.

The resultant coloured water-dissipatable polymer was dissolved inaqueous ammonia and the solution was filtered through a cascade offilters (Glass microfibre GF/A, GF/F and membrane) to 0.45 micron andthen purified by reverse osmosis using a 3000 MW cut off membrane andevaporated to dryness at approximately 80° C. to give a ColouredWater-dissipatable Polymer 3 containing a repeat unit of Formula 6:

Preparation of Ink

An ink was prepared by dissolving 10% of the Coloured Water-dissipatablePolymer 3 in a stock solution of 9 parts water and 1 part1-methyl-2-pyrrolidinone with the addition of concentrated ammonia togive a pH of 9-10. The ink was filtered through a 0.45 micron membranefilter and printed using an HP 560 thermal Ink-Jet printer. Thefollowing results (Table 4) were obtained on Gilbert Bond paper:

TABLE 4 Example 3 Run Down % Solid in Ink OD a b (5 min) 10 0.393 +30.37−13.69 10

Preparation of a Phosponic Acid Colorant of Formula 7

Meta-Aminophenylphosphonic acid (5 parts) was added to a stirredsolution of Cl Reactive Red 11 (20 parts) in water (80 parts) at roomtemperature and the resulting solution was adjusted to pH 7.0 byaddition of 2N sodium hydroxide. The solution was allowed to stir at pH7.0 and room temperature overnight and then salt was added until a solidprecipitated. The resulting suspension was filtered to give a colouredpaste and to the paste was washed with brine.

The coloured paste was dissolved in distilled water and the resultantsolution was filtered through a cascade of filters (Glass microfibreGF/A, GF/F and membrane) to 0.45 micron and then purified by reverseosmosis using a 500 MW cut off membrane and evaporated to dryness on arotary evaporator at 40° C. to leave the colorant of Formula 7 (9 parts)

Preparation of a iso-Nonylamine salt (Formula 8) of the Phosphonic AcidColorant of Formula 7

iso-Nonylamine (8 parts) was dissolved in distilled water (150 parts)and set stirring. A solution of the phosphonic acid colorant of Formula7 as prepared above (9 parts) in water (70 parts) was screened throughGF/F filter and added dropwise over 30 minutes to the solution ofiso-nonylamine, maintaining pH 7.0 by addition of 2N hydrochloric acid.The mixture was stirred for 30 minutes and then the resulting suspensionwas filtered. The collected paste was washed with water (20 parts) andthen dried at room temperature and under reduced pressure overphosphorus pentaoxide to leave a red solid (10 parts) colorant ofFormula 8.

EXAMPLE 4 Preparation of a Coloured Water-dissipatable Polymer 4

The Water-dissipatable Polymer 1 (2 parts), dicyandiamide (1.3 parts)and the colorant of Formula 8 (3 parts) were added to dimethylformamide(30 parts) and set stirring. The solution was heated to 130° C. for 72hours and then cooled to room temperature and poured onto water (300parts). The resultant suspension was adjusted to pH 10 with aqueousammonia and then the resulting solution was adjusted to pH 1 by additionof 2N hydrochloric acid. The supernatant liquid was decanted and theresulting tar-like material was dissolved in acetone (30 parts) anddiluted with water (300 parts).

The resultant suspension was adjusted to pH 10 with aqueous ammonia andthe solution was filtered through a cascade of filters (Glass microfibreGF/A, GF/F and membrane) to 0.45 micron and then purified by reverseosmosis using a 3000 MW cut off membrane and evaporated to dryness atapproximately 80° C. to give a Coloured Water-dissipatable Polymer 4containing a repeat unit of Formula 9:

Preparation of Ink

An ink was prepared by dissolving the 10% of the ColouredWater-dissipatable Polymer 4 in a stock solution of 9 parts water and 1part 1-methyl-2-pyrrolidinone with the addition of concentrated ammoniato give a pH of 9-10. The ink was then filtered through a 0.45 micronmembrane filter and printed using an HP 560 thermal Ink-Jet printer. Thefollowing results (Table 5) were obtained on Gilbert Bond paper:

TABLE 5 Example 4 Run Down % Solid in Ink OD a b (5 min) 10 0.865 +53.95−15.91 9

Preparation of Colorant of Formula 12

The 2-amino-4-phosphonicacid benzene sulphonic acid (Formula 10) (40parts) was stirred in water (600 parts) and the mixture was adjusted topH 5.0 by addition of 48% sodium hydroxide solution. The resultingsolution was cooled to 0-10° C. and 150 parts concentrated hydrochloricacid were added. To this mixture 75 parts of 2N Sodium nitrite wereadded and the mixture was allowed to stir for 10 minutes. Any excessnitrous acid was destroyed by the addition of sulphamic acid.

The pyridone (Formula 11) (42 parts) was dissolved in water (200 parts)at pH 8 by addition of 48% sodium hydroxide solution. This solution wasadded to the above mixture and adjusted to pH 5 by addition of sodiumacetate. More pyridone (Formula 11) (10 parts) was added and theresulting mixture was allowed to warm to room temperature over night.The resulting mixture was filtered to leave a paste.

The paste was dissolved in water (600 parts) and adjusted to pH 9 byaddition of ammonia and then added to concentrated hydrochloric acid (60parts) and stirred for 15 minutes and then filtered to leave a paste.The paste was dissolved in water at pH 9 by addition of ammonia and thesolution was dialysed to a Conductivity of <100 μs then filtered througha cascade of filters, (Glass microfibre, GF/A, GF/F and membrane) to0.45 micron and dried in the oven at 60° C. to give 21 parts of acolorant of Formula 12 as a yellow solid.

Preparation of an iso-Nonylamine Salt of a Colorant of Formula 12

iso-Nonylamine (20 parts) was dissolved in distilled water (700 parts)and set stirring. A solution of the colorant of Formula 10 salt (16parts) in water (300 parts) was screened through GF/F filter and addeddropwise over 30 minutes to the solution of iso-nonylamine, maintainingpH 7.0 by addition of 2N hydrochloric acid. The mixture was stirred for30 minutes and then the resulting suspension was filtered to give apaste. The collected paste was washed with water (200 parts) and thendried at room temperature and under reduced pressure over phosphoruspentaoxide for 24 hours to give the iso-nonylamine salt of colorant ofFormula 12 as a yellow solid.

Example 5 Preparation of Coloured Water-dissipatable Polymer 5

The iso-nonylamine salt of colorant of Formula 12 prepared above (80parts) and dicyanimide (20 parts) were added to a stirred solution ofWater-dissipatable Polymer 1, (100 parts) in dimethylformamide (2000parts) at room temperature. The resulting mixture was stirred for 7hours at 100° C. then cooled to room temperature and stirred overnight.

Dicyanimide (20 parts) was added and the mixture was stirred at 100° C.for 7 hours. The resulting solution was poured into water (5000 parts)and the resulting precipitate was collected by filtration and washedwith copious distilled water. The solid acid, was isolated by filtrationand washed with distilled water. The dissolving, isolation andprecipitation process was then repeated again.

The resultant coloured water-dissipatable polymer was dissolved inaqueous ammonia and the solution was filtered through a cascade offilters (Glass microfibre GF/A, GF/F and membrane) to 0.45 micron andthen purified by reverse osmosis using a 3000 MW cut off membrane andevaporated to dryness at approximately 80° C. to give a ColouredWater-dissipatable Polymer 5 containing a repeat unit of Formula 13:

Preparation of Ink

An ink was prepared by dissolving the 10% of the ColouredWater-dissipatable Polymer 5 in a stock solution of 9 parts water and 1part 1-methyl-2-pyrrolidinone with the addition of concentrated ammoniato give a pH of 9-10. The ink was filtered through a 0.45 micronmembrance filter and printed using an HP 560 thermal Ink-Jet printer.The following results (Table 6) were obtained on Gilbert Bond paper:

TABLE 6 Example 5 Run Down % Solid in Ink OD a b (5 min) 10 0.504 −15.1955.90 10

EXAMPLES 6 TO 9

Example 1 may be repeated except that in place of Water-DissipatablePolymer 1 there is used the following water-dissipatable polymer:

Example 6 MMA/Sty/MAA/HEMA 30/30/20/20

Example 7 MMA/Sty/AA/DEA 30/10/45/15

Example 8 MMA/MAA/βCEA/HPA 40/30/10/20

Example 9 MMA/Sty/MAA/HEMA/TONEM100 30/10/40/10/10

EXAMPLES 10 TO 25

Example 1 may be repeated except that in place of Cl Reactive Red 11there is used Cl Reactive Blue 81, Cl Reactive Red 2, Cl Reactive Yellow4, Cl Reactive Blue 89, Cl Reactive Brown 21, Cl Reactive Red 63, ClReactive Yellow 75, Cl Reactive Black 5, Cl Reactive Red 194, ClReactive Red 195, Cl Reactive Yellow 145, Cl Reactive Blue 173, ClReactive Orange 89, Cl Reactive Red 179, or Cl Reactive Yellow 133.

EXAMPLE 26

Further inks may be prepared having the formulations described in Tables7 and 8 below wherein the following abbreviations are used. The numberof parts by weight of each component is given. Water is included in eachformulation to make the total number of parts up to 100. These inks maybe applied to plain paper using an Ink-Jet printer.

FRU fructose CAP' 1 to 9 Identifies which of the colouredwater-dissipatable polymers as prepared in Examples 1 to 9 may be used.The number of parts by weight of CAP is shown in the second column BZBenzyl alcohol DEG Diethylene glycol DMB Diethyleneglycol monobutylether ACE Acetone IPA Isopropyl alcohol MEOH Methanol 2P 2-PyrollidoneMIBK Methylisobutyl ketone SUR Surfinol 465 (a surfactant) PHO K₂PO₄ TENtriethanolamine NMP N-methylpyrollidone TDG Thiodiglycol CAP CaprolactamBUT Butylcellosolve GLY Glycerol

TABLE 7 CAP (parts by CAP* weight) BZ DEG ACE NaOH (NH₄)₂SO₄ IPA MEOH 2PMIBK BUT 1 6 4 6 10 10 2 3 5 5 0.2 15 3 10 8 20 1 3 4 4 8 0.5 0.5 8 4 11 + 2 (4 + 4) 15 3 3 6 5 4 6 5 20 8 2 3 4 5 6 20 5 1 5 4 5 2 10 0.3 4 106 6 6 5 4 6 5 4 5 6 2 2 1 4 2 2 5 10 4 5 4 5 5 0.1 2 6 3 7 2.0 15 10 0.33 10 8 6 20 2 1 15 3 9 1.0 5 4 20 6

TABLE 8 CAP (parts by CAP* weight) BZ NMP SUR TEN TDG FRU PHO DMB CH₂NH₂CAP 4 2 5 0.15 0.4 20 6 3 6 15 0.05 4 5 10 10 0.3 15 0.2 3 1 10 20 0.50.2 2 2 8 15 15 1 5 1 5 10 10 0.2 1 4 0.2 7 3 5 3 2 6 4 10 9 7 0.5 1 5 85 11 12 8 1 3 6 5 17 7 5 5 8 5 0.1 0.2 2 0.5 0.1 5 2 2 10 5 10 5 4 8 5 89 2 9 10 4 12 1 10 10 1 1 1 1 1

What is claimed is:
 1. An ink having a viscosity less than 20 mPa.s (cP)at 20° C., comprising the components: (a) a water-dissipatable polymerwith pendant hydroxy functional groups, wherein the water-dissipatablepolymer has “number average molecular weight” less than 25,000 and isprepared by copolymerizing: i) 1 to 95% of monomers having hydroxyfunctional groups, or a group which is convertible to a hydroxyfunctional group; ii) 1 to 95% of monomers providing water-dispersinggroups; iii) 0 to 95% of monomers which are free from water-dispersinggroups and hydroxy functional groups wherein i)+ii)+iii) add up to 100;said water-dissipatable polymer having colorant attached thereto bymeans of said pendant hydroxy functional group through a covalent—O-link; and (b) a liquid medium.
 2. An ink according to claim 1 whereinthe water-dissipatable polymer is obtained by the reaction of awater-dissipatable polymer with pendant hydroxy functional groups with acolorant having a functional group capable of reacting with said pendanthydroxy functional groups.
 3. An ink according to claim 1 wherein thewater-dissipatable polymer is an olefinic polymer.
 4. An ink accordingto claim 3 wherein the olefinic polymer is obtained from thepolymerisation of 1 to 95% of olefinically unsaturated monomers havingwater-dispersing groups, 1 to 95% of olefinically unsaturated monomershaving hydroxy functional groups or a group which is convertible to ahydroxy functional group; and 0 to 95% of olefinically unsaturatedmonomers which are free from water-dispersing and hydroxy functionalgroups, wherein the amounts of said olefinically unsaturated monomersadd up to
 100. 5. An ink according to claim 1 wherein component (a) iscompletely dissipated in component (b).
 6. An ink according to claim 1which comprises from 0.5 to 50 parts of component (a) and from 50 to99.5 parts of component (b), wherein all parts are by weight and thenumber of parts of (a)+(b)=100.
 7. An ink according to claim 1 whereincomponent (b) comprises water and an organic solvent.
 8. An inkaccording to claim 7 where component (b) comprises from 40 to 95 partsof water and from 2 to 60 parts of water-miscible organic solvent.
 9. Anink according to claim 1 for use in an ink jet printer.
 10. A processfor forming an image on a substrate comprising applying thereto an inkusing an ink jet printer, wherein the ink is as defined in claim
 1. 11.A paper or an overhead projector slide printed with an ink as defined inclaim
 1. 12. An ink jet printer cartridge, optionally refillable,containing an ink as defined in claim
 1. 13. An ink according to claim1, wherein at least 85% of the pendant hydroxy functional groups arecovalently linked through —O— with the colorant.
 14. An ink according toclaim 1, wherein the water-dissipatable polymer is prepared bycopolymerizing: i) 2 to 90% of monomers having hydroxy functional groupsor group which is convertible to hydroxy functional group; ii) 5 to 90%of monomers providing water-dispersing groups; and iii) 5 to 90% byweight of monomers which are free from water-dispersing groups andhydroxy functional groups; wherein i)+ii)+iii) add up to
 100. 15. An inkhaving a viscosity less than 20 mPa.s (cP) at 20° C., comprising thecomponents: (a) a water-dissipatable polymer with pendant hydroxyfunctional groups, wherein the water-dissipatable polymer has “numberaverage molecular weight” less than 25,000 and is prepared bycopolymerizing: i) 1 to 95% of monomers having hydroxy functionalgroups, or a group which is convertible to a hydroxy functional group;ii) 1 to 95% of monomers providing water-dispersing groups; iii) 0 to95% of monomers which are free from water-dispersing groups and hydroxyfunctional groups wherein i)+ii)+iii) add up to 100; saidwater-dissipatable polymer having colorant attached thereto by means ofsaid pendant hydroxy functional group through a covalent —O-link; and(b) a liquid medium; wherein the colorant is attached to thewater-dissipatable polymer by means of a reaction between a pendanthydroxy group on the polymer with a colorant precursor thereby forming acovalent bond therebetween and subsequently converting the colorantprecursor to a colorant.
 16. An ink having a viscosity less than 20mPa.s (cP) at 20° C. comprising the components: (a) a water-dissipatablepolymer with pendant hydroxy functional groups, wherein thewater-dissipatable polymer has “number average molecular weight” lessthan 25,000 and is prepared by copolymerizing: i) 1 to 95% of monomershaving hydroxy functional groups, or a group which is convertible to ahydroxy functional group; ii) 1 to 95% of monomers providingwater-dispersing groups; iii) 0 to 95% of monomers which are free fromwater-dispersing groups and hydroxy functional groups whereini)+ii)+iii) add up to 100; said water-dissipatable polymer havingcolorant attached thereto by means of said pendant hydroxy functionalgroup through a covalent —O-link; and (b) a liquid medium; wherein thecolorant is attached to the water-dissipatable polymer by means of areaction between a pendant hydroxy group on the polymer with a bridgingcompound thereby forming a covalent bond therebetween and subsequentlyreacting the bridging compound with a colorant or colorant precursor.17. An ink according to claim 16 wherein the colorant precursor isconverted to a colorant by a diazotisation reaction.
 18. An inkaccording to claim 17 wherein the diazotisation reaction comprises: (i)diazotising an amino group in the colorant precursor using a diazotisingagent; and (ii) coupling the product of step (i) with a couplingcomponent forming an azo group there between.